The present invention is directed to recording sheets particularly suitable for ink jet printing processes. More specifically, the present invention is directed to recording sheets and to ink jet printing processes employing said sheets wherein the sheets enable the generation of high quality images and exhibit reduced or no haze in the image receiving layer thereof. One embodiment of the present invention is directed to a recording sheet which comprises a substrate and an image-receiving layer situated on at least one surface of the substrate, said image-receiving layer being suitable for receiving images of an aqueous ink, said image-receiving layer comprising (a) a binder polymer; and (b) an additive selected from the group consisting of (5-carboxy-4-hexyl-2-cyclohexen-1-yl) octanoic acid, (6-carboxy-4-hexyl-2-cyclohexen-1-yl) octanoic acid, saccharin salts, dihexyl sulfosuccinate salts, benzoate salts, monohydroxy-substituted benzoate salts, dihydroxy-substituted benzoate salts, trihydroxy-substituted benzoate salts, benzene sulfonate salts, monohydroxy-substituted benzene sulfonate salts, dihydroxy-substituted benzene sulfonate salts, benzene disulfonate salts, toluene sulfonate salts, bromobenzene sulfonate salts, xylene sulfonate salts, cumene sulfonate salts, cymene sulfonate salts, cinnamate salts, isonicotinate salts, gallate salts, piccolinate salts, hydroxynaphthoate salts, n-butylmonoglycolsulfate salts, 2-ethylhexylsulfate salts, p-aminobenzoic acid acid salts, procaine acid salts, dibucaine acid salts, caffeine, resorcinol, and mixtures thereof.
Recording sheets suitable for use in ink jet printing are known. For example, U.S. Pat. No. 5,589,277 (Malhotra), the disclosure of which is totally incorporated herein by reference, discloses a recording sheet which comprises a paper substrate and a material selected from the group consisting of monomeric amino acids, monomeric hydroxy acids, monomeric polycarboxyl compounds, and mixtures thereof. Another embodiment of the invention is directed to a recording sheet which comprises a substrate and a material selected from the group consisting of monomeric amino acids, monomeric hydroxy acids, and mixtures thereof.
European Patent Application 0 667 245 A1 (Malhotra), the disclosure of which is totally incorporated herein by reference, discloses a recording sheet which comprises a substrate and a material selected from the group consisting of monosaccharides, oligosaccharides, and mixtures thereof. Another embodiment is directed to a printing process which comprises (a) providing a recording sheet which comprises a substrate, a material selected from the group consisting of monomeric alcohols, monosaccharides, oligosaccharides, and mixtures thereof, an optional binder, an optional antistatic agent, an optional biocide, and an optional filler; (b) applying an aqueous recording liquid to the recording sheet in an imagewise pattern; and (c) thereafter exposing the substrate to microwave radiation, thereby drying the recording liquid on the recording sheet.
South African Patent Application 924,610, the disclosure of which is totally incorporated herein by reference, discloses a transparent recording sheet suitable for making visual transparencies which comprises a thin transparent film backing bearing on at least one major surface thereof an ink jet receptive layer comprising from 1% to 10% of at least one acid having a pKa of from 2 to 6, said acid being selected from the group consisting of aryl monocarboxylic acids, aryloxy monocarboxylic acids, alkyl carboxylic acids having alkyl groups containing at least 11 carbon atoms, dicarboxylic acids, tricarboxylic acids, and pyridinium salts, and at least one liquid-absorbent polymer comprising from 90% to 99% aprotic constituents, wherein said sheet shows reduced fading when imaged with an ink containing triarylmethane dye and at least one nucleophile over an identical composition containing no protic organic-solvent-soluble additive.
Copending application U.S. Ser. No. 08/657,134, filed Jun. 3, 1996, entitled "Ink Jet Transparencies," with the named inventors Shadi L. Malhotra, Kirit N. Naik, David N. MacKinnon, and Arthur Y. Jones, the disclosure of which is totally incorporated herein by reference, discloses a transparency which comprises a supporting substrate, thereover a first coating layer comprising an ink absorbing layer and a biocide, and a second ink spreading coating layer comprising a hydrophilic vinyl binder, a dye mordant, a filler, an optional lightfastness inducing agent, and an ink spot size increasing agent selected from the group consisting of hydroxy acids, amino acids, and polycarboxyl compounds; and wherein the first coating is in contact with the substrate and is situated between the substrate and the second ink coating, and which transparency possesses a haze value of from about 0.5 to about 10 and a lightfastness value of from about 95 to about 98.
D. Balasubramanian and S. E. Friberg, "Hydrotropes--Recent Developments," Surface and Colloid Science, vol. 15, E. Matijevic, ed., Plenum Press (New York 1993), p. 197, the disclosure of which is totally incorporated herein by reference, discloses background information, characteristics, and effects of hydrotropes.
While known compositions and processes are suitable for their intended purposes, a need remains for improved recording sheets. In addition, a need remains for recording sheets which are suitable for receiving images of aqueous inks, such as those commonly employed in ink jet printing. Further, a need remains for transparent recording sheets which are suitable for receiving images of aqueous inks and which also exhibit reduced or no haze. Additionally, a need remains for transparent recording sheets which are suitable for receiving images of aqueous inks, which exhibit reduced or no haze, and which enable the generation of high quality images thereon. There is also a need for opaque recording sheets wherein the image receiving coatings thereon exhibit little or no haze, thereby enabling high quality and clarity of color in images generated thereon.